Polymercaptan modified vinyl halide polymers and blends thereof with vinyl halide polymer

ABSTRACT

Vinyl halide polymers which exhibit improved processing characteristics without sacrificing physical properties are prepared by polymerizing vinyl halide monomer in the presence of an aliphatic polymercaptan having at least three mercaptan groups in an amount based on -SH equivalence of from about 0.00015 to about 0.05 equivalence -SH per mole of monomeric material. The monomer is preferably 100 percent vinyl chloride though mixtures containing a predominant amount of vinyl chloride with minor amounts of other ethylenically unsaturated monomers can also be used.

United States Patent Hwa Jan. 16, 1973 POLYMERCAPTAN MODIFIED VINYLHALIDE POLYMERS AND BLENDS THEREOF WITH VINYL HALIDE POLYMER Inventor:Jesse C. H. Hwa, Stamford, Conn.

Assignee: Staulfer Chemical Company, New

York, N.Y.

Filed: Oct. 28, 1970 Appl. No.: 84,922

Related [1.8. Application Data Division of Ser. No. 664,903, Sept. 1,1967, abandoned.

References Cited UNITED STATES PATENTS l/l968 Griffith ..260/793,219,588 11/1965 La Combe et a1 ..252/426 Primary ExaminerMurrayTillman Assistant ExaminerC. Seccuro Attorney-Robert C..Sullivan et al.

[57] ABSTRACT Vinyl halide polymers which exhibit improved processingcharacteristics without sacrificing physical properties are prepared bypolymerizing vinyl halide monomer in the presence of an aliphaticpolymercaptan having at least three mercaptan groups in an amount basedon SH equivalence of from about 0.00015 to about 0.05 equivalence -SHper mole of monomeric material. The monomer is preferably 100 percentvinyl chloride though mixtures containing a predominant amount of vinylchloride with minor amounts of other ethylenically unsaturated monomerscan also be used.

13 Claims, No Drawings POLYMERCAPTAN MODIFIED VINYL HALIDE POLYMERS ANDBLENDS THEREOF WITH VINYL IIALIDE POLYMER Cross Reference To Relatedapplication This application is a division of application Ser. No.664,903, filed Sept. l, 1967, now abandoned and refiled as Ser. No.84,470.

The present invention is directed to a process for w preparing vinylhalide polymers which exhibit improved processing characteristicswithout sacrificing physical properties. Particularly, the presentinvention relates to vinyl halide polymers prepared by polymerizing amonomer composition which is predominantly vinyl halide in the presenceof an aliphatic polymercaptan compound having at least three mercaptangroups in an amount based on SH equivalence of from about 0.00015 toabout 0.05 equivalence SH per mole of monomer in the monomer compositionmaterial. As used herein, the term per mole of monomer in the monomercomposition is intended to be based on the additive total of the numberof moles or fractions thereof of each monomer in the monomer compositionused in preparing the polymer. The term SH equivalence is intended to bebased on thenumber of functional mercaptan groups present in thepolymercaptan compound. Equivalence is computed by the followingformula:

Number-SH Amount used Molecular weight of compound Polymers formed bythe addition polymerization of vinyl halide monomers, such as vinylchloride, have gained considerable commercial importance because of thelow cost of the prepared polymer in addition to many desirable physicalproperties, such as hardness, clarity and inertness to chemicals. Whilepolyvinyl chloride has many advantages, the polymer has the disadvantageof lacking stability toward heat and light. Heat causes the degradationof the polymer, apparently by the release of hydrochloric acid to formdouble bonds on the polymer chain which are then sites forcross-linking. Free radicals are also formed in the dehydrohalogenationreaction and, in the presence of oxygen, peroxide groups are alsoformed. The total effect is to cause the polymer to blacken in color andcross-link to an infusable and useless material. The thermal stabilityof the polymer is an important factor in that polyvinyl chloride is athermoplastic polymer and therefore must be heated to the fluxing pointin order to process the polymer into useable products. At thetemperatures at which polyvinyl chloride begins to flow or flux so as toallow for processing by calendering, blow molding, or extruding, thepolymer begins to degrade. An increase in processing temperature toallow for faster processing increases the degradation rate further.While the slight degree of degradation during processing is tolerated byprocessors, it is still considered a property which desirably should beeliminated.

Polyvinyl halide polymers also have the disadvantage that they are noteasily soluble in solvents and therefore have limited use in the area ofsolution coatings, and if solution coatings are made the adherence ofthe coating to the coated substrate is generally poor. The use ofanother ethylenically unsaturated monomer, such as vinyl'acetate incombination with the vinyl chloride, can generally provide a copolymerwhich has improved solution properties but this is accomplished at thesacrifice of the desirable physical property characteristics of the purevinyl chloride type polymer.

It has now been unexpectedly found that vinyl halide polymers can beprepared which exhibit improved thermal stability and lower fluxing orflowing characteristics so as. to allow for easier processing of thepolymer without sacrificing physical properties.

It has also now been unexpectedly found that vinyl halide polymershaving improved solvent solubility can be prepared and utilized assolution coating compositions which exhibit improved adhesion to asubstrate ,without sacrificing the physical properties of the polyvinylhalide polymer.

ln accordance with the present invention, there is provided a processfor preparing vinyl halide polymers which exhibit improved processingcharacteristics and thermal stability without the loss of physicalproperties, which process comprises polymerizing in the presence of afree radical initiator an ethylenically unsaturated monomer compositioncontaining a predominant amount of vinyl halide monomer of the formula:

= equivalence in grams/mole of monomer wherein Z is hydrogen or halogenand Hal means halogen, the term halogen as used herein includingfluorine, chlorine, bromine and iodine, in the presence of an aliphaticpolymercaptan compound having at least three mercaptan groups in anamount based on SH equivalents of from about 0.000l5 to about 0.05equivalence SH per mole of monomer in the monomer composition.Surprisingly, the polymers formed are thermoplastic polymers of highmolecular weight which are characterized by physical propertiescommensurate with polymers of equal molecular weight formulated bypolymerization in the absence of the polymercaptan material with theadditional advantage that the fluxing temperature of the polymers isdecreased so as to provide improved processing characteristics and alsothe thermal stability of the polymer is increased over a polymer ofcomparable molecular weight. The decrease in fluxing temperature allowsfor the processing of the polymer under thermal conditions which areless conducive to degradation without the sacrifice of physicalproperties which the polymer is capable of providing.

The exact chemical nature of the polymer which is formed by the processof the present invention is not known. The polymercaptan is chemicallyreacted into the polymer during polymerization. ln theory, it isbelieved that the polymercaptan in some way chemically modifies thepolymeric structure, possibly by the formation of a more highly branchedpolymer than one prepared in the absence of the polymercaptan. Becauseof the amount used, the unexpected results cannot be explained on thebasis of a physical admixture wherein the polymercaptan exhibits someplasticizing effect. Also, the thermal stabilizing effect cannot beexplained on the basis of a physical admixture of thepolymercapethylenically unsaturated materials which are included withinthe limits of the formula and which are capable of entering into anaddition polymerization reaction. The polymers of the present inventioncan be formed of the same or different monomer materials falling withinthe formula and, thus, the invention is intended to cover homopolymers,copolymers, terpolymers, and interpolymers formed by the additionpolymerization of the materials falling within the formula. illustrativeof these copolymers is a copolymer of vinyl chloride and vinylidenechloride. The term vinyl halide as used in the claims is intended toinclude both homo and copolymers of compounds falling within the givenformula.

While it is preferred that the monomer composition be comprised totallyof vinyl halide monomer, the present invention is also intended toinclude copolymers formed by the free radical addition polymerizationofa monomer composition containing a predominant amount, e.g., at least50 percent of vinyl halide and a minor amount, e.g., up to 50 percent byweight of another ethylenically unsaturated monomer materialcopolymerizable therewith. Preferably, the other ethylenicallyunsaturated monomer material is used in amounts of less than 25 percentby weight and more preferably in amounts less than percent by weight ofthe total monomer materials used in preparing the polymer. Suitableethylenically unsaturated monomer materials which can be used are thosewhich can be copolymerized with the vinyl halide monomer and which donot have reactive groups which would interfere with the reactive natureof the mercaptan group and prevent the mercaptan from performing itschemical function in the reaction mixture so as to provide the desiredfinal product. Illustrative of suitable material which can be used toform copolymers, tcrpolymers, interpolymers and the like are thefollowing: monoolefinic hydrocarbons, i.e., monomers containing onlycarbon and hydrogen, including such materials as ethylene, propylene,3-methylbutene-l, 4-methylpentene-l pentene-l 3,3-dimethylbutenel4,4-dimethylbutene-l, octene-l, decene-l, styrene and its nuclear oralpha-alkyl or aryl substituted derivatives, e.g., o-, mor p-methyl,ethyl, propyl or butyl styrene; alphamet hyl, ethyl, propyl or butylstyrene; phenyl styrene; and halogenated styrenes such asalphachlorostyrene; monoolefinically unsaturated esters including vinylesters, e.g., vinyl acetate, vinyl propionate, vinyl butyrate, vinylstearate, vinyl benzoate, vinyl-pchlorobenzoates; alkyl methacrylates,e.g., methyl, ethyl, propyl and butyl methacrylate; octyl methacrylate,alkyl crotonates, e.g., octyl; alkyl acrylates, e.g., methyl, ethyl,propyl, butyl, 2- ethyl hexyl, stearyl, hydroxyethyl 'and tertiarybutylamino acrylates; isopropenyl esters, e.g., isopropenyl acetate,isopropenyl propionate, isopropenyl butyrate and isopropenylisobutyrate; isopropenyl halides, e.g., isopropenyl chloride; vinylesters of halogenated acids, e.g., vinyl alpha-chloroacetate, vinylalphachloropripionate and vinyl alpha-bromopropionate; allyl andmethallyl esters, e.g., allyl chloride, allyl cyanideyallylchlorocarbonate, allyl nitrate, allyl formate and allyl acetate and thecorresponding methallyl compounds; esters of alkenyl alcohols, e.g.,beta-ethyl allyl alcohol and beta-propyl allyl alcohol; halo-alkylacrylates, e.g., methyl alpha-chloroacrylate, ethyl alphachloroacrylate,methyl alpha-bromoacrylate, ethyl alpha-bromoacrylate, methylalpha-fluoracrylate, ethyl alpha-fluoracrylate, methylalpha-iodoacrylate and ethyl alpha-iodoacrylate; alkylalpha-cyanoacrylates, e.g., methyl alpha-cyanoacrylate and ethylalphacyanoacrylate; maleates, e.g., monomethyl maleate, monoethylmaleate, dimethyl maleate, diethyl maleate; and fumarates, e.g.,monomethyl fumarate, monoethyl fumarate, dimethyl fumarate, diethylfumarate; and diethyl glutaconate; monoolefinically unsaturated organicnitriles including, for example, fumaronitrile, acrylonitrile,methacrylonitrile, ethacrylonitrile, l,ldicyanopropene-l3-octenenitrile, crotonitrile and oleonitrile; monoolefinicallyunsaturated carboxylic acids including, for example, acrylic acid,methacrylic acid, crotonic acid, 3-butenoic acid, cinnamic acid, maleic,fumaric and itaconic acids, maleic anhydride and the like. Amides ofthese acids, such as acrylamide, are also useful. Vinyl alkyl ethers andvinyl ethers, e.g., vinyl methyl ether, vinyl ethyl ether, vinyl propylether, vinyl n-butyl ether, vinyl isobutyl ether, vinyl 2-ethylhexylether, vinyl 2-chloroethyl ether, vinyl cetyl ether and the like; andvinyl sulfides, e.g., vinyl B-chloroethyl sulfide, vinyl B-ethoxyethylsulfide and the like can also be included. Diolefmically unsaturatedhydrocarbons containing two olefinic groups in conjugated relation andthe halogen derivatives thereof, e.g., butadiene- 1,3;2-methyl-butadiene-l,3; 2,3-dimethyl-butadiene- 1,3; 2-chloro-butadienel,3; 2,3-dichloro-butadienel 3; and 2-bromo-butadiene-l ,3 and the like.

Specific monomer compositions for forming copolymers can be illustratedby vinyl chloride and/or vinylidene chloride and vinyl acetate, vinylchloride and/or vinylidene chloride and maleic or fumaric acid esters,vinyl chloride and/or vinylidene chloride and acrylate or methacrylateester, vinyl chloride and/or vinylidene chloride and vinyl alkyl ether.These are given as illustrative of the numerous combinations of monomerspossible for the formation of copolymers. The present invention isintended to cover all such combinations which fall within the scope ofthe present invention. While these combinations are intended to beincluded within the scope of the presentinvention, it is aliphaticwherein the free bonds of the carbon atom can be at- N iimberSfigroups/compound 7 Amount of compound used monomer used in forming thefinal polymer. Polymers can be prepared in accordance with the presentinvention by utilizing quantities of a polymercaptan compound sufficientto provide an SH equivalence of from about 0.000l5 to about 0.05equivalence SH per mole of monomer used to form the final polymer.Equivalency is computed in accordance with the following formula:

Molecular weight of compound tached to aliphatic, aromatic or inorganicmoieties and n is an integer of 3 and above. Thus, the polymercaptanincludes aliphatic as well as aralkyl types. The polymercaptan compoundcan have a straight chain or branched chain molecular configuration. Thecompound can be symmetrical or unsymmetrical with regard to the SHfunctionality. The mercaptan group can be attached to a primary,secondard or tertiary car bon atom. Other functional groups, forexample, ester groups, ether groups, amide groups, hydroxy groups, andthe like, may also be present provided that they do not interfere withthe reactive nature of the mercaptan group and prevent the mercaptangroup from performing its chemical function in the reaction mixture soas to provide the desired final product. The polymercaptan compound canalso be a low molecular weight polymer having at least three pendantmercaptan groups per molecule. The molecular weight of the polymericpolymercaptan is desirable less than 3,000 for ease of use in thepolymerization.

Illustrative of the various mercaptan containing moieties which moietiescan comprise all or part of the mercaptan containing moieties which formthe aliphatic polymercaptan compound for use in the present inventionare:

SH); Q-R-SH;

and the like wherein R is aliphatic and preferably an alkyleneradicaLThese are given only as illustrative of the various mercaptancontaining moieties which can be present either alone or in combinationin the polymercaptan compound. Other moieties not specifically mentionedwhich are within the generic description of the polymercaptan areintended to be included within the scope of the present invention.

Any desired polymercaptan compound may be used alone or in admixturewith other polymercaptan compounds with equal facility. Therefore, it isintended that the term polymercaptan compound as used herein include notonly pure polymercaptan compounds but also admixtures of variouspolymercaptans.

The amount of polymercaptan compound used in the process of the presentinvention is based on the functional equivalency of the mercaptan groupsper mole of captoacetate),

in grams/mole of monomer The above formula can be used to directlycompute the SH equivalence of a single polymercaptan compound. Theequivalence of admixtures. of different polymercaptans are obtained bydetermining the equivalence for each polymercaptan using the aboveformula followed by adding the equivalence from each to obtain the totalSH equivalence of SH groups present during the polymerization.Preferably, the SH equivalence is maintained within the range of about0.000l5 to about 0.005, and more preferably within the range of about0.0003 to about 0.002 SH equivalence per mole of monomer.

Suitable polymercaptan materials can be illustrated by pentaerythritoltri(7-mercaptoheptanoate), pentaerythritol tetra(7-mercaptoheptanoate),mercaptoacetic acid triglyceride, pentaerythritoltri(beta-mercaptopropionate), pentaerythritoltetra(beta-mercaptopropionate), cellulose tri(alpha-mercaptoacetate),l,2,3-propane-trithiol, l,2,3,4-neopentane-tetrathiol,l,2,3,4,5,6-mercaptopoly(ethylneoxyethyl)sorbitol), l,l l trimethylpropane tri(alpha-mercaptoacetate), dipentaerythritolhexa(3-mercaptopropionate), 1,2,3- tris(alpha-mercaptoacetyl) propane,thiopentaerythritol tetra(alhpa-mercaptoacetate 1,6,10-trimercaptocyclododecane, l ,2,3,4,5,6-hexamercaptocyclohexane, N,N,N,N"-tetra(2-mercaptoethyl)pyromellitamide,tri-(2-mercaptoethyl)nitrilotriacetate, pentaerythritoltri(alpha-merpentaerythritol tetra(alpha-mercaptoacetate),tri(p-mercaptomethylphenyl)methane, 2,2,7,7-tetrakis(mercaptomethyl)-4,5dimercaptooctane, 5,5,5-tri(mercaptoethyl)phosphorotrithioate, xylitolpenta (beta-mercaptopropionate), and the like.

illustrative of low molecular weight polymeric materials having at leastthree pendant mercaptan groups per molecule are homopolymers andcopolymers of vinyl thiol, e.g., polyvinyl thiol. Other polymericthiols, such as glycerol/ethylene glycol polyether polymercaptan canalso be used.

It is preferred to use low molecular weight monomeric materials havingfrom three to five mercaptan groups per molecule as illustrated bypentaerythritol tetrathioglycolate, pentaerythritoltetra(3-mercaptopropionate). trimethylolethanetri(3-mercaptopropionate), xylitol penta( beta-mercaptrithioglycolate,and

with the method of the present invention, be accomplished using mass,suspension, emulsion or solution techniques, though the use ofthesuspension technique is preferred. The various additives andconditions as used in such polymerication procedures are also useable inthe operation of the method of the present invention. Variation ofconditions of reaction depending on the type of monomer composition,catalyst or initiator system and type of procedure are within thepurview of a skilled artisan.

Mass or bulk polymerization is initially a single phase reactioncomprising the monomer and a monomer soluble catalyst or initiator.Preferably, and in the practice of the method of the present invention,a polymercaptan, such as 1,2,3-propanetrithiol, which is soluble in themonomer phase is used. Since mass polymerizations are highly exothermic,the reaction mixture should be vigorously agitated during thepolymerization reaction to assist in heat dissipation so as to preventthe polymerization reaction from running away. Mass polymerizationgenerally is conducted in the absence of any additives other than afree-radical initiator and hence is advantageous for the preparation ofpolymers having a minimum degree of contamination.

Suspension polymerization refers to the polymerization of monomerdispersed in a suspension medium which is a non-solvent for both themonomer and the polymer, generally water, utilizing, normally, a monomersoluble initiator. Suspension polymerization is similar to masspolymerization in that polymerization takes place within a monomer phasecontaining a monomer soluble initiator. However, the use of thesuspension medium assists in the dissipation of the heat or reaction andtherefore the polymerization reaction is easier to control. Suspensionpolymerization is generally accomplished by dispersing the monomer inthe suspending medium either by constant agitation, by use of asuspending agent, preferably both. Various suspending agents such asgelatin, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropylcellulose, carboxymethyl cellulose, talc, clay, polyvinyl alcohol andthe like can be used in the suspension polymerization of vinyl halideand these agents can be used in the method of the present invention.Other suspending agents which are known to be useful in the suspensionpolymerization of vinyl halides can also be used. The type and amount ofthe suspending agent used has, as is known, some influence on theparticle size of the finally obtained product. The exact amounts ofsuspending agent and type can be selected by the skilled artisan so asto provide the particle'size of product desired. Various otheradditives, such as thermal stabilizers, and the like, which are normallyutilized in the polymerization can also be included. Suspensionpolymerization techniques are generally preferred in that thepolymerization is easier to conduct. and the product obtained has aparticle size which is more easily handled and used by polymerprocessors.

Emulsion polymerization refers to the polymerization of a monomerdispersed in an aqueous medium utilizing a water soluble catalyst orinitiator and an emulsifying agent to maintain the monomer in itsemulsified form. Emulsion polymerization differs from suspensionpolymerization in that the initiator in the emulsion polymerization isgenerally'wi'tliin the aqueous phase whereas the initiator in"thesuspension polymerization is generally within the monomer phase.

In theory, the kinetics of the two types of polymerization seem toproceed along entirely different lines. Another distinction is that theemulsion polymerization provides polymer particles within the range of0.1 p. to 5 11. whereas the suspension polymerization provides muchlarger particles of product within the range of l0 [L to l,000 1,.Various emulsifying agents such as sodium lauryl sulfate, potassiumstearate, alkyl benzene sulfonate, ammonium dialkyl sulfosuccinate areknown for use in polymerizing vinyl halides by emulsion techniques andcan be used in the practice of the present invention. Other emulsifyingagents which are also known to be useful in emulsion polymerization ofvinyl halides can also be used. The exact amounts of the emulsifyingagent and a type which is used are easily determined by the skilledartisan. In general, any of the additives such as catalysts andstabilizers, which are normally used in emulsion polymerization of vinylhalides can be utilized in the practice of the present invention. Theproduct obtained from the emulsion polymerization which is in the formof a latex can be utilized per se or the latex can be coagulated toprecipitate the polymer particles which can then be dried and processedinto any desired form by polymer processor.

Solution polymerization is a process which requires the use of an inertliquid which is a solvent for the monomeric compounds used in formingthe polymer which solvent may or may not be a solvent for the preparedpolymer. The catalyst or initiators, if used, are of the same types asthose used in the mass polymerization reaction. Solution polymerizationhas the advantage that the solvent, as in suspension polymerization,assists in the dissipation of the heat of reaction. The averagemolecular weight of polymers prepared by the use of solutionpolymerization techniques are generally lower than those obtained by theuse of other polymerization techniques and this method can be effectivein the production of low molecular weight vinyl halide polymers. Ingeneral, any of the additives such as catalysts and stabilizers whichare normally used in solution polymerization of vinyl halides can beutilized in the practice of the present invention. The polymer isusually separated from the solvent and the solvent is recycled so as tomake the process more economical. The solvents which are used insolution polymerization can be those in which only the monomer issoluble and those in which both the monomer and resulting polymer aresoluble, the former solvents being preferred. Illustrative of themonomer soluble, polymer insoluble solvents which can be used in theperformance of a solution polymerization of vinyl halides are: pentane,hexane, benzene, toluene and cyclohexane. Illustrative ofmonomer-polymer solvents which can be used in the solutionpolymerization of vinyl halides are: cyclohexanone, tetrahydrofuran,dimethyl sulfoxide, and dimethyl formamide. A mixture of solvents canalso be used to reduce cost, e.g., as by the use of an expensive solventdiluted with an inexpensive non-solvent or weak solvent. Illustrative ofsolvent mixtures are: tetrahydrofuran and toluene or petroleum ether.The foregoing solvents and mixtures are given as illustrative and are inno way intended to be inclusive of all the possible solvents andmixtures thereof which can be utilized.

The polymerization of the vinyl halide monomers is a free-radicalpolymerization reaction and should be conducted in the presenceofafree-radical initiator. Useful free-radical initiators are organic orinorganic peroxides, persulfates, ozonides, hydroperoxides, peracids andpercabonates, azo compounds, diazonium salts, diazotates,peroxysulfonates, trialkyl borane-oxygen systems, and amine oxides.Azodiisobutyronitrile is particularly useful in the present invention.The catalyst is used in concentrations ranging from about 0.01 to about1.0 percent by weight based on the total weight of the monomers. For usein mass, suspension, and solution polymerization, the catalysts whichare soluble in the organic phase, such as benzoyl peroxide, diacetylperoxide, azobisisobutyronitrile or diisopropyl peroxydicarbonate,.azobis (a-methyl-y-carboxybutyronitrile), caprylyl peroxide,lauroylperoxide, azobisisobutyramidine hydrochloride, r-butylperoxypivalate,2,4-dichlorobenzoyl peroxide,azobis('a-ydimethylvaleronitrile) are generally used. For use inemulsion polymerization, water soluble catalysts such as ammoniumpersulfate, hydrogen peroxide are used. Preferably, the initiator whichis used is chosen from a group of initiators known in theprior art asthe hot catalysts or those which have a highdegree of freeradicalinitiating activity. lnitiators with a lower degree of activity are lessdesirable in that they require longer polymerization times. Also, longpolymerization times may cause preliminary product degradation evidencedby color problems, e.g., pinking. Other known free radical initiatingcatalysts, such as light illumination or irradiation with gamma-ray canalso be used. Catalysts which tend to cause ionic or coordinationpolymerization such as the Ziegler-type catalysts can be used in thepresent invention if organic solvents are used as the reaction medium.

The polymerization of the monomers'is conducted at temperatures varyingbetween 80 C. to about 120 C. for varying periods of time depending onthe type of monomers utilized and the polymerization technique employed.The choice of a specific reaction temperature is dependent to a largeextent on the initiator which is utilized and the rate of polymerizationwhich is desired. Generally, for suspension polymerizations,temperatures of about40 C. to 70 C. in the presence of an azo typeinitiator have been found to be effective.

it has also been found that the relative viscosity of the polymer can beaffected by temperature. As the temperature increases, the relativeviscosity of the. polymer decreases. In theory, as the temperatureincreases so does the polymerization rate and therefore, the polymertends to be more highly branched and have shorter polymer chains. it hasbeen further found that the relative viscosity of the polymer isdependent on temperature and concentration of polymercaptan. Thus, byvarying both temperature and concentration of polymercaptan, polymers ofvarying relative viscosities can be obtained and this provides greaterlatitude in the choice of polymerization conditions.

The time necessary for conducting a polymerization reaction againdepends on the type of monomer, the temperature, and the type ofinitiator which are chosen. The amount of time necessary to effect acompletion of a polymerization reaction is well within the purview of askilled artisan following his choice of monomer initiator andpolymerization system.

in any of the foregoing polymerization procedures, any other additiveswhich are now commonly utilized can be.included within thepolymerization mixture. Other procedures such as short-stopping the.polymerization at a desired.- point can-also be utilized in EXAMPLESSuspension Polymerization Procedure In Examples 1 to '10, the followingsuspension polymerization procedure is used unless otherwise indicated:The'reaction mixture or charge is sealed in a 1 quart soda bottle, thebottle is immersed in a temperature controlled water bath, and thepolymerization is conducted for 14 hours. The bottles are rotated endover end at 41 revolutions per-minute in the bath to provide agitation.Conversion is usually about percentto about percent. The charge consistsof the following materials in amounts given in approximate parts byweight:

Charge I Parts by Weight (Dry) Vinyl Chloride l00 Deionized Water 230Polymer'captan See Table l suspending Agent 0.167

Initiator 0.067

Parts by weight of a commercially available blend of polymercaptanscontaining: 35% Pentacrythritol tetra( 3-mcrcaptopropionatc) 35% Pcntaerythritol tri( J-mcrcaptopropionatc) HydroxymcthylcelluloseAzohisisobutyronitrile TABLE I Polymercaptan SH equiv- Reactiontemperature and relative alence viscosity per Parts mo1e of A B C D bmono- Exampie weight mer 44 C. 47 C. 51 C 60 C The polymerizationprocedure set forth above operates equally as well to provide thedesired final product when other suspending agents, e.g., gelatin,polyvinyl alcohol, hydroxypropyl cellulose, carboxymethyl cellulose,hydroxyethyl cellulose, talc and clay, are used in place of thehydroxymethyl cellulose. Similarly, the azobisisobutyronitrile initiatorcan be replaced by lauroyl peroxide, diisopropylperoxy dicarbonate, ort-butyl peroxypivalate initiators.

The approximation of actual processing conditions and the determinationof the processability of a polymer can be done in a laboratory by meansof a fusion torque rheometer. The polymer in powdered form is placed inthe instrument and is fused under the influence of heat and shear. Theinstrument, which is basically in dynamometer, measures the torque forcerequired to maintain mixer rotors revolving at a constant speed whilethe polymer is being fused. The instrument comprises a heated rotorcavity of measured size having rotors of the Banbury mixer type mountedtherein. The rotors are driven by an electric motor suspended betweentwo bearing blocks through which extends the main shaft of the motor. Aweighted balance bar is attached to the motor to compensate for mitCorp., Rahway, NJ.) and 0.5 part by weight of a lubricant (calciumstearate). Values reported for fusion torque rheology are in meter-gramsand are for equilibrium torque. The values for stability are the thetorque force required in operating the rotors. At-. number of minutesthat the polymer-remains at the tached to the balance bar is a weightmeasuring device equilibrium point before degrading. Those with a pluswhich can be read visually and which is provided with a indicate thatthe test was conducted for the given scribe for recording measuredweights on a sheet of number of minutes and that no gross failure inphysical recording paper. A tachometer and control circuit is propertiesdue to degradation (blacking, etc.) of the used to maintain the numberof revolutions of the ropolymer samples had occurred during that time.The tors constant. A circulatory oil temperature control type of failureresults corresponds to the rate ranges system is used to control thetemperature within the given hereinbefore. The table also gives relativerotor cavity. The test comprises inserting a measured viscosity valuesand tensile strength values. 7

' TABLE II Equillb- Stability rlum melt at equilib- Parts vis. in riumpolymer- Relative metermelt in Tensile Example captan viscosity gramsminutes Typeot failure. Strength 0.0 2.02 1,800 18 Catastrophic 7.7000.1 1.82 1,500 Non-catastrophic 0.2 1.72 1,320 100 do 0.3 1.71 1,170 60+..do. D 0.5 1.58 900 100+ -do Conventional polyvinyl chloridehomopolymers:

Med. mol. wt--.. 0.0 2.12 2,220 29 Catastrophic 7,790 Low mol wt 0.01.78 1,500 43 Semi-catastrophic... 7,490 0.0 1.61 1,260 as ...do 7,440

NoTE.-Relative viscosity is measured at 30 C. using 1 gram of polymerdissolved inlOO grams of cyclohexa none in a Ubbelohde viscoslmeter.

amount of polymer in powdered form into the rotor cavity and measuringthe resistance torque on the rotors developed by the sample as it beginsto melt. This resistance causes the electric motor to swing in adirection opposite the direction of shaft rotation. This swinging motionis transmitted by the balance bar to the weight measuring device whichdetermines the number of meter-grams of reverse force necessary tooffset the swinging motion and hence the torque being applied to therotors. The torque generally rises from a low point when the sample ofpolymer is in powdered form to a high point at flux after which thetorque subsides to an intermediate equilibrium point or equilibriumtorque. The torque remains constant until the polymer degrades whereuponthe torque increases due to polymer crosslinking. The equilibrium torquevalue determines. the amount of work in meter-grams which must beapplied to the polymer to process the same. The length of time thepolymer remains at the equilibrium torque point before degrading is ameasure of the thermal stability of the polymer. Another valueindicativeof stability is the rate of degradation as measured inmeter-grams per minute. The faster the degradation, the less stable isthe polymer. As used herein, polymers which degrade at a rate of from025 meter-grams per 1 minute are denoted as having failednon-catastrophically, 25 to I00 meter-grams per minute assemicatastrophically and 100 meter-grams per minute and above ascatastrophically. ln thefollowing Table II are reported values forfusion torque rheometer measurements made on the polymers of Examples2D, 3D, 4C, 6D compared with the rheometer values of a control samplefrom Example iD. Rheometer values for a The polymers of the presentinvention also begin to fuse faster than conventional polyvinyl chloridehomopolymer and they reach the equilibrium melt point in less time.

As can be seen from a comparison of the data in Table ll, it can be seenthat the polymers of the present invention have lower torque rheologyvalues than the control prepared under similar conditions. Also, it canbe. seen that the torque rheology values for the polymers of the presentinvention are lower than conventional polyvinyl chloride homopolymershaving approximately the same relative viscosity. These rheology valuesindicate that the polymers of the present invention require less work toprocess than comparable polyvinyl chloride homopolymers, e.g., moreeasily processable. Also, and since the equilibrium torque point isrelated to both temperature and shear, the polymers of the presentinvention can be processed at shear rates comparable to conventionalpolyvinyl chloride homopolymers of the same approximate relativeviscosity but at a lower temperature. Either case provides an area ofeconomic saving for the polymer processor.

Also, the table shows that the polymers of the present invention havemuch longer stability times as compared to the control and comparablemedium and low molecular weight conventional polyvinyl chloridehomopolymers. These longer stability times allow the processor more timeto work the'polymer and therefore make the limits of working time lesscritical.

The tensile strengths of the final products prepared from the listedpolymers are, as can be seen in the table, substantially equal. Thisindicates that physical properties have not been sacrificed to obtain aneasier processing polymer.

The polymers prepared in accordance with the present invention alsoexhibit increased solvent solubility and, when applied as solutioncoatings, are more adherent to the coated base. Also, solution coatingsof the polymers of the present invention require less baking or dryingto develop an adherent coating than comparable polymers not made inaccordance with the invention.

The following are examples of the solvent solubility of a vinyl chloridepolymer prepared in accordance with the method of Example 3D which has arelative viscosity of 1.66 (Polymer A) compared to a polyvinyl chloridehomopolymer having a relative viscosity of 1.78 (Polymer B). Viscositiesin centipoises are determined at 25 using a Brookfield viscosimeter 24hours after the solutions are prepared.

EXAMPLE 7 grams of Polymer A are dissolved in 85 grams of cyclohexanonewith stirring at room temperature. The procedure is repeated usingPolymer B, e.g., the polyvinyl chloride homopolymer. The viscosities areshown in Table lll.

EXAMPLE 8 10 grams of Polymer A are dissolved in 90 grams of methylethyl ketone with stirring at 60 C. the procedure is repeated usingPolymer B, e.g., the polyvinyl chloride homopolymer. The viscosities areshown in Table III.

EXAMPLE 9 l 1 grams of Polymer A are dissolved in a mixture of 10 gramsof cyclohexanone and 40 grams of methyl ethyl ketone at 60 C. withstirring. 50 grams of toluene are stirred in to form a clear solution.The procedure is repeated using Polymer B, e.g., the polyvinyl chloridehomopolymer. The viscosities are shown in Table HI.

PVC Homopolymer Solutions in mixed solvents prepared in accordance withExample 9 are applied to metallic test panels using a 6 mil draw-downbar. The panels are then air dried for l5-20 seconds and then are driedfor a controlled period of time in a recirculating air oven. Adhesiontests are then conducted to determine if the drying time is sufficientto provide an adherent film. Adhesion is determined on the coated panels24 hours after removal from the oven using the cellophane tape test. Inthis test, the coating is cross-hatched with a sharp knife to thesubstrate, the lines being one-sixteenth inch apart. Cellophane tape isfirmly pressed on the scored area and is rapidly pulled away from thecoating. Ratings of the test are as follows:

Excellent No coating removed. Good Very slight coating removal at knifemarks. Fair Some coating removal. Poor Considerable coating removal.Very Poor Total removal of coating.

TABLE IV Polymer of Temperature Tlme Example 3D PVC Base 1. Aluminumcoated with chromic phosphate and oxides at level of 8-l 2 mg./sq.ft.425 F. l5 sec. VP VP 425 F. 30 sec. E VP 425 F. 45 sec. E P 425 F. 60sec. E P

Base 2. Aluminum coated with chromium oxide and aluminum oxide. 425 F.l5 sec. E P 425 F. 30 sec. E E 425 F. sec. E E 425 F. 60 sec. F. E

Base 3. Steel coated with zinc phosphate having internal crystal refinmgagent at level of l-275 mgJsq. ft. 425 F. l5 sec. VP VP 425 F. 30 sec.F-P VP 425 F. 45 sec. G VP 425 F. sec. E VP Base 4. Steel coated withaccelerated iron phosphate at levels of 50-l 20 mg./sq.ft. 425 F. l5sec. P-F P 425 F. 30 sec. F-G VP 425 F. 45 sec. E P-F 425 F. 60 sec. E

Base 5. Electrolytic tin plate. 425 F. 60 sec. F-G VP 300 F. l0 min. E EBase 6. Cold rolled steel. 300 F. 10 min. E P

As the above data indicates, coatings applied from solutions containingthe polymers prepared in accordance with the present invention requireless drying time to develop excellent adhesion than coatings ofcomparable polyvinyl chloride homopolymer. Also, the polymers preparedin accordance with the invention allow for the preparation of, moreadherent coatings than those of a comparable polyvinyl chloridehomopolymer.

The polymers of the present invention can also be advantageously used inblends with other polymer materials such as polyvinyl chloridehomopolymers. The polymercaptan modified polymers of the inventionprovide a blended polymer material having a reduced equilibrium torquevalue and an increased thermal stability time as compared to the purepolyvinyl chloride homopolymer which is used in forming the blends.Also, the polymers of the present invention provide a polymer blendwhich has increased toughness as compared to the toughness of the purehomopolymer used in forming the blend. The increased toughness isdirectly attributable to the blend in that comparisons with polyvinylchloride homopolymers of the same equilibrium torque as the blend showthat products formed from the blended polymer material are tougher thanthose of the pure homopolymer. The amount of the polymer of the presentinvention which is blended is dependent on the results desired.Generally, as little as about 25 percent by weight and as much as aboutpercent by weight based on the total weight of the blend can be used. A50/50 blend has been found to be highly effective. The following Table Vgives comparative results of toughness tests applied to conventionalhomopolymers and to a blend of one of the homopolymers with a polymer ofthe present invention.

The test utilized in compiling the data is an ASTM test titled TensileImpact Energy to Break Plastics and Electrical Insulating Materials"which is designated D l822-6lT. Basically, a polymer sample in the shapeof a dumbbell or a bone type dog biscuit is clamped to a free swingingpendulum. The other end of the sample is clamped in a crosshead clampwhich is of greater width than the pendulum. An anvil composed of twoblocks separated a sufficient width to allow the pendulum to passtherebetween but not the crosshead clamp is provided and is attached toa standardized tension impact machine. The energy to fracture the sampleby shock in tension is determined by the kinetic energy developed at theinstant the travel of the crosshead is arrested during the process ofbreaking the sample. The energy absorbed in the break is reported infoot-pounds per square inch of minimum cross-sectional area of thesample. Also important in this test is the manner in which the samplebreaks and the number of such breaks; If the sample breaks clean with nostress whitening or elongation, it is denoted a brittle break and isindicative of the brittleness of the polymer. if the sample showselongation and stress whitening at the break, it is denoted a ductilebreak and is indicative of the ductility or toughness of the polymer.lf, out of 10 samples, a majority of breaks are brittle, the polymer isconsidered brittle and if.a majority are ductile, the polymer isconsidered ductile. Also, the energies absorbed in breaking the sampleshow the toughness of the polymer in that low absorbed energy valuesindicate a brittle polymer and high absorbed energy values indicate aductile or tough polymer.

I 7 TABLE v radical polymerization. In other words, a branched polymerhaving long polymer chain branches is formed. Molecular weightdeterminations further support this theory. Absolute molecular weightvalues are obtained using light scattering photometry which issubstantially unaffected by polymer structure. Other methods ofobtaining molecular weight values, such as gel permeation chromatography(GPC) and solution viscosity are affected by polymer structure and thesetests give relative numbers based on molecular size or hydrodynamicvolume, e.g., the. space occupied by the polymer molecule. These testsgive apparent molecular weight. A molecule ofa branched polymer of thesame molecular weight as a molecule of a linear polymer would be morecompact and thus have a smaller hydrodynamic volume. Theoretically, theabsolute molecular weight and the apparent molecular weight of a linearpolymer should be the same and the absolute molecular weight FusionTensile impact rheometer equivalent Brittle Energy Ductile EnergyPolymer Torque Stability breaks absorbed breaks absorbed 1 Polymer 01present invention (A) 1, 080 00+ 8 24 2 101 Conventional PVC homopolymerrel. vis. 2.12"... 2, 220 2 24 7 150 3 Conventional PVC homopolymer rel.vis. 1.78. l, 500 43 7 20 2 122 50/50 blend of 1 and 2 1, 560 52 0 0 10133 Nora-(A) A polymer prepared in accordance with the procedure ofExample 3D having a relative viscosity of 1.68.

Chemical analysis has failed to elucidate the exact structure of thepolymer formed by the process of the present invention. Within thelimits of experimental accuracy of the chemical analysis tests, variousfacts have been uncovered which give an indication as to the structureof the polymer which is formed. It is to be understood that thefollowing data is subject to experimental error and limitation and isnot to be considered absolute. The indications of structure based on theexperimental analysis data are to be considered only as theory and aregiven only to provide a possible explanation for the results obtained bythis invention.

Sulfur analysis tests'indicate that substantially all of the mercaptosulfur is present in the finally prepared polymer. Titrations to detectfree mercaptan groups indicate the absence of free mercaptan groups inthe polymer. Because of the small quantities of polymercaptan used andthe limitations of the test asto sensitivity, the absence of freemercaptan groups is not to be considered absolute. Mass spectrometry andthin layer chromatography tests did not show the presence of anyunreacted polymercaptan in the polymer. Tests for disulfide linkagesalso proved negative. Tests were also conducted on the polymer ofExample 3D which was prepared using a polymercaptan having estercarbonyl linkages to determine if the structure of the polymercaptancompound was affected during polymerization. These tests also provednegative. Since the polymercaptan used ,in Example 3D is based onpentaerythritol, tests were also conducted to determine whether or notthe neopentyl group of the pentaerythritol remained in the polymer. Apositive result was obtained in these tests. The foregoing dataindicates that the polymercaptan is reacted with and incorporated intothe polymer. In theory, a polymer structure is formed which has as itscentral moiety the residue of the polymercaptan and polymerchainsextending from each sulfur atom as it is known that mercaptohydrogen atoms from a monomercaptan compound can be removed duringpolymerization to form a free radical at the sulfur site and hence asite for free seen, the ratio of absolute to apparent molecular weightis l for the conventional polyvinyl chloride homopolymers indicating alinear polymer whereas the ratio for the polymer of the presentinvention is L4 indicating a branched polymer.

TABLE VI Absolute moi. Apparent weight molecular weight Ratio, Relativeby light absolute/ Polymer viscosity scattering GPC Viscosity apparentPolymer of present inventi 1. 88 64 63 1. 4 1. 78 65 65 66 1. 0 2.12 J898 92 1. 0

NorE.-Tl1o above molecular weight numbers are multiplied by 1,000 toobtain actual molecular weight value.

Thus, and in theory, analytical data seems to indicate the formation ofa branched polymer by the incorporation of the polymercaptan into thepolymer. The foregoing is theory and applicant presents the foregoingonly as a possible explanation of the results obtained in performing theprocess of the present invention and applicant does not intend to bebound thereby.

EXAMPLE 10 Using the aforedescribed suspension polymerization procedure,a polymer is prepared wherein the initiator is azobisisobutyronitrile,the suspending agent is hydroxymethyl cellulose and wherein 0.218 parts(0.00103 SH equivalence per mole of monomer) of trimethylolpropanetri(3-mercaptopropionate) is used as the polymercaptan.

EXAMPLE 1 1 Using the suspension polymerization procedure at 60 C.,, apolymer is prepared wherein the initiator is tbutyl peroxypivalate, thesuspending agent is gelatin and wherein 0.2 parts (0.00103 SHequivalence per mole of monomer) of pure tetramercaptopentaerythritol isused as the polymercaptan.

EXAMPLE 12 Using the suspension polymerization procedure at 60 C., apolymer is prepared wherein the initiator isdiisopropylperoxydicarbonate, the suspending agent is polyvinyl alcoholand wherein 0.06 parts (0.00063 SH equivalence per mole of monomer) of1,3,5-trimercaptocyclohexane is used as the polymercaptan.

EXAMPLE 13 Using the aforedescribed suspension polymerization procedureat 8 C., a polymer is prepared wherein the initiator isazobisisobutyronitrile, the suspending agent is hydroxymethyl celluloseand wherein 0.214 parts (0.0016 -SH equivalence per mole of monomer) ofdipentaerythritol hexa(3mercaptopropionate) is used as thepolymercaptan. A good yield of polymer having a relative viscosity of l.87 is obtained.

EXAMPLE 14 A polymer is prepared using the aforedescribed suspensionpolymerization procedure at 58 C. wherein the initiator isazobisisobutyronitrile, suspending agent is hydroxymethyl cellulose andwherein 1.5 parts (0.001 SH equivalence per mole of monomer) ofpolyvinyl thiol having a molecular weight of about 480 and having anaverage of eight mercaptan groups per molecule is used as thepolymercaptan.

EXAMPLE 15 A polymer is prepared by repeating Example 12 using areaction vessel having an inlet valve. The charge with the exception ofthe polymercaptan is placed in the vessel and polymerization isinitiated. The polymercaptan is incrementally added through the inletvalve to the reaction vessel during the first hour of reaction.

Polymers are also prepared using the aforedescribed suspensionpolymerization procedure and using the following materials:

Example l6 0.196 parts (0.0010 SH equivalence per mole of monomer) ofN,N', N", N"'-tetra(2-mercaptoethyl) pyromellitamide.

17 0.117 parts (0.0008 SH equivalence per mole of monomer oftri(2-mercaptoethyl) nitriloacetate.

18 155 parts of vinylidene chloride 1.6 moles) in place of the 100 partsvinyl chloride used in Example 3D.

19 90 parts vinyl chloride and 15.5 parts vinylidene chloride (moleratio 9/1) in place of the 100 parts vinyl chloride used in Example 3D.

20 parts vinyl chloride and 13.75 parts vinyl acetate (mole ratio 9/1)in place of the parts vinyl chloride used in Example 3D.

21 80 parts vinyl chloride, 15.5 parts vinylidene chloride and 27.5parts diethyl fumarate (mole ratio 8/1/1) in place of the 100 partsvinyl chloride used in Example 3D.

22 0.189 parts (0.001 SH equivalence per mole of monomer) of xylitolpenta(beta-mercaptopropionate) Emulsion Polymerization Procedure Thereaction mixture or charge containing the monomer initiator emulsifyingagent, polymercaptan and water is sealed in a 1 quart soda bottle, thebottle is immersed in a constant temperature bath and the mixture isallowed to react for 14 hours. The bottle is rotated end over end at 41revolutions per minute to provide the agitation necessary effectemulsification. The charge consists of the following materials inamounts given in approximate parts by weight:

Parts by Weight (Dry) Vinyl Chloride 100 Deionized Water 230 SodiumLauryl Sulfate 2.0 Potassium Persulfate 0.1 Sodium Bicarbonate 0.05Polymercaptan EXAMPLE 23 Using the emulsion polymerization procedure at58 C., a stable latex is obtained at 100 percent monomer conversionusing as polymercaptan 0.1 parts of the polymercaptan blend which isused and described in Examples 2 to 6. The latex is coagulated by dryingto obtain polymer having a relative viscosity of 1.99. Replacement ofthe potassium persulfate/sodium bicarbonate initiator system with coppersulfate/hydrogen peroxide or potassium persulfate/potassiummetabisulfite/Fe initiator systems provides equal results. Otheremulsifying agents such as sodium ethylhexyl sulfate and sodiumdi-n-hexylsulfosuccinate can be used in place of the sodium laurylsulfate with equal facility.

Solution Polymerization Procedure The reaction mixture or charge issealed in a 1 quart soda bottle, the bottle is immersed in a constanttemperature bath and the mixture is allowed to react for 14 hours. Thebottle is rotated end over end at 41 revolutions per minute to provideagitation. The charge consists of the following materials in amountsgiven in approximate parts by weight:

Parts by Weight (Dry) Vinyl Chloride 100 Hexane 200Azobisisobutyronitrile 0.1 Polymercaptan EXAMPLE 24 Using the solutionpolymerization procedure at 58 C., a polymer is prepared using aspolymercaptan 0.2 parts of the polymercaptan blend used and described inExamples 2 to 6. Polymer particles precipitate from the vinylchloride/hexane solution as formed. Polymer particles are separated fromthe reaction mixture by filtration and dry to a fine white powder. Equalresults can be obtained using other organosoluble initiators such aslauroyl peroxide, diisopropylperoxydicarbonate and tbutyl peroxypivalatein place of the azobisisobutyronitrile initiator. Also, otherhydrocarbon solvent systems, such as: pentane, benzene, toluene,cyclohexanone, cyclohexane, tetrahydrofuran, dimethyl sulfoxide,dimethyl formamide and mixtures thereof can be used. Mass or BulkPolymerization Procedure The reaction mixture or charge is sealed in a 1quart soda bottle, the bottle is immersed in a constant temperature bathand the polymerization reaction is allowed to proceed for approximately2% hours (approximately 20 to 35 percent monomer conversion). Thereaction is stopped by chilling the bottle in cold water and then dryice followed by venting any remaining monomer. Agitation duringpolymerization is provided by rotating the bottle end over end at 41revolutions per minute. The charge consists of the following materialsin amounts given in approximate parts by weight:

Parts by Weight (Dry) Vinyl Chloride 100 Azobisisobutyronitrile 0.1Polymercaptan EXAM PLE 25 Using the bulk polymerization procedure at 50C., a polymer is prepared using 0.2 parts of the blend of polymercaptansas used and described in Examples 2 to 6. A fluffy white powder isobtained. Substitution of the azobisisobutyronitrile initiator withother organo-soluble initiators such as lauroyl peroxide,diisopropylperoxydicarbonate or t-butyl peroxypivalate provides similarresults.

Using the aforedescribed emulsion, solution or bulk polymerizationprocedures, polymers are obtained using:

Example 26 0.109 parts (0.00053 SH equivalence per mole of monomer) oftrimethylolpropane tri(3- mercaptopropionate).

27 0.2 parts (0.00103 SH equivalence per mole of monomer) oftetramercaptopentaerythritol.

28 0.06 parts (0.00063 SH equivalence per mole of monomer) ofl,3,S-trimercaptocyclohexane.

29 0.214 parts (0.0016 SH equivalence per mole of monomer) ofdipentaerythritolhexa(3- mercaptopropionate).

30 1.5 parts (0.001 SH equivalence per mole of monomer of polyvinylthiol having a molecular weight of about 480 and an average of abouteight mercaptan groups per molecule.

31 0.196 parts (0.0010 SH equivalence per mole of monomer of N,N, N",N"'-tetra(2-mercaptoethyl) pyromellitamide.

32 0.117 parts (0.0008 SH equivalence per mole of monomer) oftri(Z-mercaptoethyl) nitriloacetate.

33 155 parts of vinylidene chloride (1.6 moles) in place of the 100partsvinyl chloride using the polymercaptan described in Example 3D.

34 90 parts vinyl chloride and 15.5 parts vinylidene chloride (moleratio 9/1 in placeof the 100 parts vinyl chloride using thepolymercaptan described in Example 3D.

35 parts vinyl chloride, 15.5 parts vinylidene chloride and 27.5 partsdiethyl fumarate (mole ratio 8/1/1) in place of the 100 parts vinylchloride using the polymercaptan described in Example 36 parts vinylchloride and 13.75 parts vinyl acetate (mole ratio 9/1) in place of theparts vinyl chloride using the polymercaptan described in Example 3D.

37 0.189 parts (0.001 SH equivalence per mole of monomer) of xylitolpenta(beta-mercaptopropionate).

38 80 parts vinyl chloride and 41.5 parts monomethyl maleate (8/2 moleratio) in place of the 100 parts vinyl chloride using the polymercaptandescribed in Example 3D.

39 90 parts vinyl chloride and 16 parts ethyl acrylate (9/1 mole ratio)in place of the 100 parts vinyl chloride using the polymercaptandescribed in Example 3D. v

40 90 parts vinyl chloride and 8.5 parts acrylonitrile (9/1 mole ratio)in place of the 100 parts vinyl chloride using the polymercaptandescribed in Example 3D.

41 90 parts vinyl chloride and 11.5 parts vinyl ethyl ether (9/1 moleratio) using the polymercaptan described in Example 3D.

The foregoing examples have illustrated the method of the presentinvention using vinyl chloride and vinylidene chloride as the vinylhalide monomer. Other vinyl halide monomers such as vinyl bromide, vinyliodide, vinylidene bromide,vinylidene iodide and mixtures thereof can besubstituted for the vinyl chloride with equal facility. Vinyl fluorideand vinylidene fluoride which have very low vapor pressures can also beused in high pressure polymerization vessels.

Various copolymers and terpolymers using non-vinyl halide type monomersin combination with the vinyl halide monomer has also been illustrated.Any other non-vinyl halide monomer such as those listed heretofore canbe substituted with equal facility to prepare copolymers andterpolymers.

The polymers prepared in accordance with the present invention can beused in applications such as the preparation of calendered film, blowmolded bottles, estruded flat bed and blown film, extruded articles,tubing, in injection molding, fluidized bed coating, electrostaticpowder spraying, rotational casting, foamed back vinyl flooring as aplastisol replacement, as a fabric coating, as a paper impregnatingsolution, as metallic surface coating solutions, additives to otherpolymers to increase toughness of the resulting blend or whereverpolyvinyl chloride is presently used. lt is understood that the polymersof the invention and their solvent solutions can be compounded withadditives usually employed in the coating, impregnating and moldingcomposition arts.

Thus, andin accordance with the present invention, there is provided amethod for the preparation of a new class of vinyl halide polymers whichexhibit improved processing characteristics, improved thermal stabilitywithout sacrificing physical properties and which polymers provideunexpected advantages when used in the formation of solution coatingcompositions and when blended with other polymer materials.

What is claimed is:

1. An improved vinyl halide polymer composition comprising from about 25percent to about 75 percent by weight of a first vinyl halide polymerprepared by the free radical polymerization of an ethylenicallyunsaturated monomer composition containing more than 90 percent byweight based on the total weight of said monomer composition of vinylhalide of the formula:

n Halogen V wherein Z is hydrogen or halogen and less than percent ofanother ethylenically unsaturated comonomer copolymerizable therewith inthe presence of an aliphatic polymercaptan compound having at leastthree mercaptan groups per molecule wherein the mercaptan group isattached to the remainder of the molecule by means of aliphatic carbonof the formula:

the free bonds of the carbon atom being attached to aliphatic, aromaticor inorganic moieties and n being an integer of at least 3, saidpolymercaptan compound being present during polymerization in an amountbased on --SH equivalence of from 0.00015 to about 0.05 equivalence -SHper mole of monomer in said monomer composition, and from about 75percent to about 25 percent by weight of a second polyvinyl halidepolymer not prepared in the presence of the aforesaid polymercaptan.

2. The vinyl polymer composition as recited in claim 1 wherein saidvinyl halide forming said first polymer is selected from the groupconsisting of vinyl chloride, vinylidene chloride and mixtures of vinylchloride and vinylidene chloride.

3. The vinyl halide polymer composition as recited in claim 1 whereinsaid monomer forming said first polymerconsists of 100 percent vinylhalide monomer. 4. The vinyl halide polymer composition as recited inclaim 3 wherein said vinyl halide monomer forming said first polymer isvinyl chloride.

5. The vinyl halide polymer composition as recited in claim 1 whereinsaid comonomer is selected from the group consisting of mono-olefinichydrocarbons; diolefinic hydrocarbons, styrenes, halosubstitutedstyrenes, monoethylenically unsaturated mono and dicarboxylic acidsincluding their esters, amides, nitriles and halosubstitutedderivatives; and monovinyl ethers, divinyl ethers and their thio ethers.

6. The vinyl halide polymer composition as recited in claim 1 whereinsaid polymercaptan compound has from three to five mercaptan groups permolecule.

7. The vinyl halide polymer composition as recited in claim 1 whereinsaid polymercaptan is a low molecular weight polymeric polymercaptanmaterial having a molecular weight of up to about 3,000, and at leastthree mercaptan groups per molecule.

8. The vinyl halide polymer compositions as recited in claim 1 whereinsaid polymercaptan is selected from the group consisting ofpentaerythritol tetra-(3-merca to to ionate entae thritol tri 3-mercatogrogiori ate); penf erythr itol tetrathi glycolat trimethylolethanetri (3-mercaptopropionate); trimethylolethane trithioglycolate;trimethylolpropane tri (3-mercaptopropionate); trimethylolpropanetrithioglycolate; and mixtures thereof.

9. The vinyl halide polymer composition as recited in claim 1 whereinsaid polymercaptan is used in an amount of from about 0.00015 to about0.005 equivalence Sl-l per mole of monomer in said monomer compositionfor said first polymer.

10. The vinyl halide polymer composition as recited in claim 1 whereinsaid polymercaptan is used in an amount of from about 0.0003 to about0.002 equivalence SH per mole of monomer in said monomer composition forsaid first polymer.

11. The vinyl halide polymer composition as recited in claim 1 whereinsaid free radical polymerization is conducted using suspensionpolymerization techniques.

12. The vinyl halide polymer composition as recited in claim 1 whereinsaid second polymer is a polyvinyl chloride homopolymer.

13. The vinyl halide polymer composition as recited in claim 12 whereinthe said composition consists of about 50 percent by weight vinyl halidepolymer and about 50 percent polyvinyl chloride homopolymer.

2. The vinyl polymer composition as recited in claim 1 wherein saidvinyl halide forming said first polymer is selected from the groupconsisting of vinyl chloride, vinylidene chloride and mixtures of vinylchloride and vinylidene chloride.
 3. The vinyl halide polymercomposition as recited in claim 1 wherein said monomer forming saidfirst polymer consists of 100 percent vinyl halide monomer.
 4. The vinylhalide polymer composition as recited in claim 3 wherein said vinylhalide monomer forming said first polymer is vinyl chloride.
 5. Thevinyl halide polymer composition as recited in claim 1 wherein saidcomonomer is selected from the group consisting of mono-olefinichydrocarbons; diolefinic hydrocarbons, styrenes, halosubstitutedstyrenes, monoethylenically unsaturated mono and dicarboxylic acidsincluding their esters, amides, nitriles and halosubstitutedderivatives; and monovinyl ethers, divinyl ethers and their thio ethers.6. The vinyl halide polymer composition as recited in claim 1 whereinsaid polymercaptan compound has from three to five mercaptan groups permolecule.
 7. The vinyl halide polymer composition as recited in claim 1wherein said polymercaptan is a low molecular weight polymericpolymercaptan material having a molecular weight of up to about 3,000,and at least three mercaptan groups per molecule.
 8. The vinyl halidepolymer compositions as recited in claim 1 wherein said polymercaptan isselected from the group consisting of pentaerythritoltetra-(3-mercaptopropionate); pentaerythritol tri(3-mercaptopropionate);pentaerythritol tetrathioglycolate; trimethylolethane tri(3-mercaptopropionate); trimethylolethane trithioglycolate;trimethylolpropane tri (3-mercaptopropionate); trimethylolpropanetrithioglycolate; and mixtures thereof.
 9. The vinyl halide polymercomposition as recited in claim 1 wherein said polymercaptan is used inan amount of from about 0.00015 to about 0.005 equivalence -SH per moleof monomer in said monomer composition for said first polymer.
 10. Thevinyl halide polymer composition as recited in claim 1 wherein saidpolymercaptan is used in an amount of from about 0.0003 to about 0.002equivalence -SH per mole of monomer in said monomer composition for saidfirst polymer.
 11. The vinyl halide polymer composition as recited inclaim 1 wherein said free radical polymerization is conducted usingsuspension polymerization techniques.
 12. The vinyl halide polymercomposition as recited in claim 1 wherein said second polymer is apolyvinyl chloride homopolymer.
 13. The vinyl halide polymer compositionas recited in claim 12 wherein the said composition consists of about 50percent by weight vinyl halide polymer and about 50 percent polyvinylchloride homopolymer.